Method for controlling rotational speed of motor of fan

ABSTRACT

A method for controlling a rotational speed of a motor of a fan is provided in the present application, applicable to an air cleaner and including: calculating a suitable rotational speed range according to a space size of a use environment and a filter gauze type of the air cleaner; calculating a suitable rotational speed according to air quality sensed by a sensor or air quality information; subsequently, adjusting a rotational speed offset according to a relatively high or a relatively low rotational speed preferred by a user; checking whether a range at present is a timing enhancement range; determining that the rotational speed is not higher than a noise upper limit rotational speed; and setting a rotational speed of a motor of a fan.

BACKGROUND Technical Field

The present application relates to a method for controlling a rotationalspeed of a motor of a fan, and in particular, to a method forcontrolling a rotational speed of a motor of a fan applicable to an aircleaner. The rotational speed of the motor is adjusted according to airquality obtained by sensing a surrounding environment by a sensordisposed on the air cleaner or air quality information.

Related Art

Generally, when air quality is poor, a cleaner needs to accelerate itsoperation to quickly clean the air; when air quality is good, thecleaner can operate at a lower speed or stop operating to save energy.Because the air quality changes with time or occurrence of some events,for example, opening a window, smoking, cooking, or burning incense, therotational speed of the cleaner needs to be adjusted accordingly.

Usually, a user can manually adjust the wind speed, but the userprobably cannot always pay attention to the air quality and quicklyadjust the rotational speed. On the other hand, the user probably cannotperceive that the air quality has deteriorated and how poor the airquality has become, because particles in air are invisible to naked eyesand some organic gases are colorless and odorless and cannot be detectedby humans. Therefore, an effective method is to build a sensor in thecleaner. When the sensor detects that the air quality changes, therotational speed of the cleaner is appropriately adjusted in response tothe change in the air quality.

At present, most cleaners having a built-in sensor on the market supportsuch an automatic operation mode, which is referred to as a conventionalautomatic operation mode herein. In the conventional automatic operationmode, generally, there is a fixed correspondence for adjusting therotational speed of the motor of the fan of the cleaner according to airquality detected by the sensor of the cleaner. For example, assumingthat the air quality is divided into four levels (or more or lesslevels), the motor operates at a fixed rotational speed of, for example,400 rpm when the air quality is at the first level (best quality), at afixed rotational speed of 700 rpm when the air quality is at the secondlevel, at a fixed rotational speed of 1000 rpm when the air quality isat the third level, and at a fixed rotational speed of 1300 rpm when theair quality is at the fourth level (worst quality). Although this methodis more convenient that the manner in which a user manually adjusts therotational speed of the motor according to the air quality, thecorrespondence between the air quality and the rotational speed is notthe most appropriate most of the time or cannot truly meet userrequirements. Specific cases are provided below.

1. When the cleaner is placed in spaces of different sizes and under asame air condition, if same air quality is expected to be maintained,the cleaner should have different rotational speeds because differentquantities of air need to be cleaned. However, in the conventionalautomatic operation mode, a same rotational speed is used. 2. Even ifthe cleaner is placed in a same space, the cleaner has different aircleaning capabilities (CADR: Clean Air Delivery Rate) when usingdifferent types of cleaner filter gauzes. To achieve a same cleaningrate, when different types of cleaner filter gauzes are used in the caseof same air quality, the cleaner should have different rotationalspeeds. However, in the conventional automatic operation mode, a samerotational speed is used. 3. Even if the cleaner is placed in a samespace and uses a same filter gauze, because some people may feed a petat home, or have a child having allergies at home, or are quitesensitive to dirty air, and prefers the automatic operation mode butexpect a higher rotational speed, the conventional automatic operationmode cannot meet such a personal requirement. 4. In addition, in somespecial places, for example, a hospital, a studio, and a chemicallaboratory, in addition to the conventional automatic operation mode,the user expects that the cleaner is capable of accelerating operationfor a period of time at intervals regardless of the air quality and thenreturning to the automatic mode. The conventional automatic operationmode cannot meet such a special requirement. 5. Some users buy more thanone cleaner and place them at different positions in a large space, forexample, one in a kitchen and one in a living room. When cooking isperformed in the kitchen and the cleaner in the living roomautomatically operates, the cleaner not only refers to its own sensor,but may also refer to a sensor of another cleaner specified by the user,for example, a sensor of the cleaner in the kitchen. The cleanerscooperate to quickly filter air until the air in the entire living roomand kitchen are clean. The conventional automatic operation mode cannotmeet the requirement of such cooperative operation. 6. If a window of ahouse is often open, when outdoor air quality deteriorates, the cleaneralso needs to increase the rotational speed accordingly. In theconventional automatic operation mode, the rotational speed cannot beautomatically adjusted according to the outdoor air quality. 7. Someusers have the elderly and children who like a relatively quietenvironment at home. Therefore, such users expect that when the cleanerautomatically operates, even if air quality is very poor, the cleanerdoes not operate too loudly. The conventional automatic operation modecannot meet such a personal requirement.

Therefore, for determining of a rotational speed in the automaticoperation mode, the rotational speed needs to be adjusted not onlyaccording to air quality sensed by a sensor of the cleaner, but morefactors such as a room size and a filter gauze type also need to bereferred to. In addition, special personal requirements such asaccelerated operation, an intermittent acceleration, and a noise upperlimit need to be met. Moreover, outside information is referred to bytaking advantage of networking, to fully use benefits of the automaticoperation mode. Only in this case can the automatic operation mode bethe most intelligent one and best meet personal requirements.

SUMMARY

An objective of the present application is mainly to provide a methodfor controlling a rotational speed of a motor of a fan of an aircleaner. A space environment is sensed by a sensor, to control arotational speed of a motor of a fan of an air cleaner based on apersonal preference and requirement. In this way, an automatic operationmode of the air cleaner is smarter and more intelligent.

The method for controlling a rotational speed of a motor of a fan isprovided in the present application. The method is applicable to an aircleaner and comprises: calculating a suitable rotational speed rangeaccording to a space size of a use environment and a filter gauze typeof the air cleaner; calculating a suitable rotational speed according toair quality sensed by a sensor or air quality information, where the airquality information may be current air quality information on thenetwork; adjusting a rotational speed offset according to a relativelyhigh or a relatively low rotational speed preferred by a user; checkingwhether a range at present is a timing enhancement range; determiningthat the rotational speed is not higher than a noise upper limitrotational speed; and setting a rotational speed of a motor of a fan.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is Steps S100 to S150: a method for controlling a rotationalspeed of a motor of a fan

DETAILED DESCRIPTION

To further understand the objective, structural features, and functionsof the present application, descriptions are provided in detail withreference to related embodiments and FIGURES as follows:

In the conventional automatic operation mode, there is a fixedcorrespondence between air quality and the rotational speed of the motorof the fan. For example, there are four levels of air quality: good,ordinary, not good, and very poor, and corresponding fixed rotationalspeeds of the motor of the fan are: 400 rpm, 700 rpm, 1000 rpm, and 1300rpm. The rotational speed is always 400 rpm, 700 rpm, 1000 rpm, or 1300rpm regardless of the size of a space in which a cleaner is placed. Ascan be learned, assuming that the air quality is not good and therotational speed is 1000 rpm, a relatively small space quickly becomesclean again, but in a relatively large space, a user needs to tolerateunclean air for a relatively long time. Is there any way for therelatively large space to quickly become clean again as the relativelysmall space?

In fact, the relatively large space can quickly become clean again asthe relatively small space as long as the cleaner considers a space sizewhen determining a rotational speed as the air quality is not good. Therotational speed is relatively low when the space is small, and therotational speed is relatively high when the space is large. In thisway, spaces of different sizes may become clean again within a sameperiod of time.

Second, a cleaning capability of the cleaner is related to a filtergauze type. Different filter gauzes usually correspond to different CADRvalues of the same cleaner. For example, using a PM2.5 filteringcapability as an example, a pure HEPA filter gauze usually has a betterfiltering capability than that of a compound filter gauze of a samesize. Filter gauzes made of filtering materials of different filteringlevels have different filtering capabilities. Certainly, a filter gauzeis selected based on different considerations. Once the filter gauze isselected, when the rotational speed of the motor of the fan isdetermined, a filtering capability of the filter gauze needs to beconsidered, so that a same cleaning speed can be reached.

Therefore, after the air quality is determined, the cleaner needs tocalculate a suitable rotational speed of the motor according to thespace size and the filter gauze type.

How to determine the air quality? Is a sensor of the cleaner the onlyreference? Theoretically, air quality at each position in a space willfinally be the same. However, in fact, how fast will the same airquality be achieved is related to the space size and efficiency of aircirculation. Therefore, if more sensors are placed in the space, the airquality in the space can be detected more accurately than the case whereonly one sensor is used.

Using this concept as a starting point, the cleaner needs to refer toanother sensor in the same space when determining the air quality.

Values of another sensor may be obtained by various means such as anetwork or other extended connection, as long as the values can beobtained.

After the values are obtained, final air quality may be determined byusing different policies, for example, a minimum (MIN) policy or aweighted averaging policy.

In short, after the air quality is determined, the suitable rotationalspeed of the motor may be calculated according to the space size and thefilter gauze type.

In addition, values of another nearby sensor may be used as referencesof the air quality, the cleaner may alternatively obtain outdoor airquality by using the network. If a user also expects to refer to theoutdoor air quality to determine a rotational speed of the motor, theoutdoor air quality may also be referred to when the final air qualityis determined.

An automatic operation mode has various advantages. If the user prefersa quicker cleaning effect, or a quieter and more energy-saving effect,can both effects be achieved? Yes, both of the effects can be achievedas long as the cleaner additionally considers a user's personalpreference and accelerates or decelerates the rotational speed whendetermining a rotational speed. In this way, the rotational speed notonly can be automatically determined but also satisfies the personalpreference.

Another requirement is that, on one hand, the cleaner is expected to becapable of operating automatically; on the other hand, the cleaner isexpected to be capable of accelerating operation for a period of time atintervals regardless of the air quality. Can the requirement be met?Yes, the requirement can be met as long as the cleaner checks whether an“enhancement range” arrives before determining the final rotationalspeed. If the “enhancement range” arrives and the rotational speed isnot enough, the cleaner increases the rotational speed and therequirement is met.

Finally, if the user does not expect too much noise of the cleanerregardless of the air quality, can the rotational speed of the cleanerbe kept not exceeding a “noise upper limit” that can be tolerated by theuser? Yes, the rotational speed can be kept not exceeding the noiseupper limit as long as it is checked, when the final rotational speed isdetermined, whether the rotational speed exceeds a noise upper limitrotational speed set by the user. If the rotational speed exceeds thenoise upper limit rotational speed, the rotational speed is limited.

In the conventional automatic operation mode, the rotational speed isdetermined only according to the air quality sensed by the sensorwithout considering that the rotational speed needs to be adjustedaccording to the space size and the filter gauze type. In addition,unique personal requirements such as a personal preference for therotational speed (preference for quicker filtering or being quieter), arequirement for timing enhancement, and too much noise are notconsidered. Information of an external sensor is not referred to bytaking advantage of networking to enable the cleaners to operatecollaboratively to more quickly react to a change in the air quality andmore quickly clean a larger place. The method for automaticallycontrolling a rotational speed of a motor of a fan provided by thepresent application meets all these requirements.

The method for controlling a rotational speed of a motor of a fan of anair cleaner of the present application includes: first, step S100:Calculate a suitable rotational speed range according to a space sizeand a filter gauze type of the use environment of the cleaner. That is,according to a corresponding filter gauze type, the cleaner may detect aquantity of air that can be cleaned within a unit of time, referred toas a clean air delivery rate (CADR), and a rotational speed fan-CADR ofthe fan of the cleaner under such a CADR condition. Information samplingincludes:

1. According to space size information A (square meter) provided by auser, assuming that a space height is H meters, a sundries rate in thespace is p (0<p<1), air in the space is filtered for a maximum of T-maxtimes per hour, and air in the space is filtered for a minimum of T-mintimes per hour, a highest rotational speed of the fan is recommended tobe:

fan-max=fan-CADR×A×H×(1−p)×T-max/CADR  (formula 1)

2. A lowest rotational speed is recommended to be:

fan-min=fan-CADR×A×H×(1−p)×T-min/CADR  (formula 2)

Step S110: Calculate a suitable rotational speed according to airquality sensed by a sensor. A main calculating sampling manner is asfollows:

Because values of the sensor has a lot of disturbance and errors, it isnot necessary to adjust the rotational speed of the fan each time whenthe value changes. A relatively appropriate method is to divide thevalues of the sensor into several ranges N, for example, six ranges.Each range corresponds to one air quality level.

The cleaner may have one or more sensors, for example, one PM2.5 sensor,one PM10 sensor, and one TVOC sensor. Values of another external sensormay alternatively be referred to by means of user setting. An outdoorair quality index may alternatively be referred to. Before therotational speed of the fan is determined, comprehensive air qualityneeds to be first determined.

Each value of the sensor corresponds to one air quality range.Certainly, different types of sensors have different correspondencemanners. In the present application, an air quality index (AQI) is usedas an example. As shown in Table 1 (a reference data source:https://en.wikipedia.org/wiki/Air_quality_index), PM2.5 and PM10 cancorrespond to the air quality ranges as follows:

TABLE 1 part I O₃ (ppb) O₃ (ppb) PM_(2.5) (μg/m³) PM₁₀ (μg/m³)C_(low)-C_(high) C_(low)-C_(high) C_(low)-C_(high) C_(low)-C_(high) AQI(avg) (avg) (avg) (avg) Category   0-54 (8-hr) 0.0-12.0 (24-hr)   0-54(24-hr) Good  55-70 (8-hr) 12.1-35.4  55-154 (24-hr) Moderate (24-hr) 71-85 (8-hr) 125-164 (1-hr) 35.5-55.4 155-254 (24-hr) Unhealthy for(24-hr) Sensitive Groups  86-105 (8-hr) 165-204 (1-hr)  55.5-150.4255-354 (24-hr) Unhealthy (24-hr) 106-200 (8-hr) 205-404 (1-hr)150.5-250.4 355-424 (24-hr) Very Unhealthy (24-hr) 405-504 (1-hr)250.5-350.4 425-504 (24-hr) Hazardous (24-hr) 505-604 (1-hr) 350.5-500.4505-604 (24-hr) Hazardous (24-hr) part II CO (ppm) SO₂ (ppb) NO₂ (ppb)C_(low)-C_(high) C_(low)-C_(high) C_(low)-C_(high) AQI AQI (avg) (avg)(avg) I_(low)-I_(high) Category  0.0-4.4 (8-hr)   0-35 (1-hr)   0-53(1-hr)  0-50 Good  4.5-9.4 (8-hr)  36-75 (1-hr)  54-100 (1-hr)  51-100Moderate  9.5-12.4 (8-hr)  76-185 (1-hr) 101-360 (1-hr) 101-150Unhealthy for Sensitive Groups 12.5-15.4 (8-hr) 186-304 (1-hr) 361-649(1-hr) 151-200 Unhealthy 15.5-30.4 (8-hr) 305-604 (24-hr) 650-1249(1-hr)  201-300 Very Unhealthy 30.5-40.4 (8-hr) 605-804 (24-hr)1250-1649 301-400 Hazardous (1-hr) 40.5-50.4 (8-hr) 805-1004 (24-hr)1650-2049 401-500 Hazardous (1-hr)

For other sensors, a similar correspondence manner may be used, as longas quantities of corresponding ranges are the same. Different policiesmay be used to determine the comprehensive air quality. The worst airquality is used as reference, or weighted averaging is used: Differentweighted values are allocated to different sensors. In short, after thecomprehensive air quality is determined, assuming that the air qualityfalls in an n^(th) range (1<=n<=N), the rotational speed of the fanfan-n is:

fan-n=fan-min+(fan-max−fan-min)×(n−1)/(N−1)  (formula 3).

Subsequently, step S120: Adjust a rotational speed offset according to arelatively high or a relatively low rotational speed preferred by auser. The user may accelerate or decelerate the rotational speedfan-offset because a family member has allergies or a pet is fed athome, or because of a personal preference of a quicker cleaning effect,a personal preference of a more energy-saving and quieter effect, oranother personal preference. In this case, the rotational speed becomes:fan-n+fan-offset.

Subsequently, step S130: Check whether a range at present is a timingenhancement range. In some special places, for example, a clinic or astudio, a user may force a cleaner to operate at a relatively highrotational speed fan-boost for m minutes at an interval of M minutes. Ifthe range falls in the “m” range, the rotational speed is:

fan-n′=max of((fan-n+fan-offset),fan-boost)  (formula 4).

Subsequently, step S140: Determine that the rotational speed is nothigher than a noise upper limit rotational speed, and set a rotationalspeed of a motor of a fan. That is, finally, before the rotational speedof the motor is set, it needs to be determined that the rotational speedof the fan is not higher than the noise upper limit rotational speedfan-noise. Therefore, a final rotational speed is fan-final=min of(fan-n′, fan-noise) (formula 5).

Finally, step S150: Set a motor of a fan according to fan-final. Itshould be noted that, fan-n′ may be greater than an upper limit of therotational speed of the motor of the fan, but fan-noise definitelycannot exceed the upper limit of the rotational speed of the motor;therefore, fan-final cannot exceed the upper limit of the rotationalspeed of the motor.

In addition to the smart function and personal preferences mentionedabove, the following can also be combined: 1. Scheduling: The cleaner ispowered on or off at a specified time according to a personalrequirement. 2. Sleeping: At a scheduled time, the cleaner enters asleep mode. In the sleep mode, the following parameters can be set: LEDluminance, a personally preferred rotational speed offset, a noise upperlimit rotational speed, and the like.

As described above, implementations of the present application are asfollows:

It is assumed that there are three types of filter gauzes of thecleaner, values of the CADR that correspond to the filter gauzes andthat are measured at a rotational speed of fan-CADR=1300 rpm arerespectively 150 CMH, 200 CMH, and 250 CMH (m³/h). An upper limit of therotational speed of the cleaner is fan-max=1300 rpm, and a lower limitis fan-min=200 rpm. The air quality is divided into 6 levels. At thesame time, it is assumed that the height of a room is H=2.4 m, thesundries rate is p=0.3, air in the space is filtered for a maximum ofT-max=5 times per hour, and the air in the space is filtered for aminimum of T-min=1 time per hour.

Example 1

The size of the room is A=20 square meters, the filter gauze is a filtergauze 2, and the CADR=200 CMH.

1. According to formula 1:fan-max=fan-CADR×A×H×(1−p)×T-max/CADR=1300×20×2.4×(1−0.3)×5/200=1092.

2. According to formula 2:fan-min=fan-CADR×A×H×(1−p)×T-min/CADR=1300×20×2.4×(1−0.3)×1/200=218.4.

3. In this case, a PM2.5 value of the sensor of the cleaner is 20 μg/m³and corresponds to the air quality in the second range according toTable 1. In addition, the cleaner also refers to an external PM2.5sensor (such as an air quality detector). A value of the external PM2.5sensor is 40 μg/m³ and the air quality is in the third range accordingto Table 1. The cleaner also refers to a local outdoor PM2.5 value andthe value is 5 μg/m³. The air quality is in the first range according toTable 1. If the air quality is evaluated by using the minimum (MIN)policy, the comprehensive air quality falls in the third range.According to formula 3: fan-n=fan-min+(fan-max−fan-min)×(n−1)/(N−1),fan-3=218.4+(1092−218.4)×(3−1)/(6−1)=567.84 (rpm).

4. If the user has a child and also feeds three cats at home, and theuser expects the cleaner to be capable of cleaning indoor air morequickly, the user accelerates the rotational speed fan-offset=100 rpm.In this case, the rotational speed becomes: fan-3+fan-offset=667.84(rpm).

5. In addition, the user personally has a relatively high requirement onair quality, and hopes that the cleaner can accelerate operation for 3minutes at an interval of 10 minutes, and fan-boost set by the user isfan-boost=900 rpm. Therefore, if the cleaner has not entered anacceleration range, the rotational speed maintains 667.84 rpm; if thecleaner at present is in the acceleration range, as shown in formula 4,the rotational speed is increased to 900 rpm. Assuming that the cleanerhas not entered the acceleration range, the rotational speed is 667.84rpm.

6. A value of the noise upper limit set by the user personally isfan-noise=1100 rpm. Because the rotational speed at present does notexceed fan-noise, as shown in formula 5, the rotational speed is 667.84rpm.

7. Finally, the motor of the fan is set to the rotational speed.

An objective of the present application is mainly to provide a methodfor controlling a rotational speed of a motor of a fan of an aircleaner. A space environment is sensed by a sensor, to control therotational speed of the fan of the motor of the air cleaner according toair quality and air quality information and based on a personalpreference and requirement, where the air quality information is currentair quality information on the network. In this way, an automaticoperation mode of the air cleaner is smarter and more intelligent.

In conclusion, the foregoing descriptions are only intended to recordthe implementations or embodiments of technical means used to resolveproblems in the present creation, but are not intended to limit theimplementing scope of the present creation. That is, any equivalentchanges and modifications consistent with the meaning within theapplication scope of the present creation or made according to the scopeof the present creation shall fall within the scope of the presentcreation.

What is claimed is:
 1. A method for controlling a rotational speed of amotor of a fan, applicable to an air cleaner and comprising thefollowing steps: calculating a rotational speed range according to aspace size of an environment and a filter gauze type; calculating arotational speed in the rotational speed range according to air qualitysensed by a sensor or air quality information; and adjusting therotational speed according to a rotational speed offset.
 2. The methodfor controlling a rotational speed of a motor of a fan according toclaim 1, further comprising: determining whether a range is a timingenhancement range to enhance the rotational speed.
 3. The method forcontrolling a rotational speed of a motor of a fan according to claim 2,further comprising: determining that noise generated by the rotationalspeed is not higher than a noise upper limit rotational speed, andsetting a final rotational speed.
 4. The method for controlling arotational speed of a motor of a fan according to claim 3, wherein therotational speed range comprises a highest fan rotational speed and alowest fan rotational speed, an area of the space is A square meters, aheight of the space is H meters, a sundries rate in the space is p, airin the space is filtered by a maximum of T-max times per hour, the airin the space is filtered for a minimum of T-min times per hour, aquantity of air that can be cleaned by the filter gauze within each unittime is a clean air delivery rate (CADR), a fan rotational speed underthe CADR condition is fan-CADR, and the highest fan rotational speedfan-max is:fan-max=fan-CADR×A×H×(1−p)×T-max/CADR, and the lowest fan rotationalspeed fan-min is:fan-min=fan-CADR×A×H×(1−p)×T-min/CADR.
 5. The method for controlling arotational speed of a motor of a fan according to claim 3, whereinvalues sensed by the sensor is divided into N ranges, the air qualityfalls in an n^(th) range in the N ranges, and the rotational speed fan-nis:fan-n=fan-min+(fan-max−fan-min)×(n−1)/(N−1).
 6. The method forcontrolling a rotational speed of a motor of a fan according to claim 3,wherein a cleaner operates at a relatively high rotational speedfan-boost for m minutes when the enhancement range is at an interval ofM minutes, and the rotational speed is:fan-n′=max of((fan-n+fan-offset),fan-boost).
 7. The method forcontrolling a rotational speed of a motor of a fan according to claim 3,wherein the noise generated by the rotational speed is determined not tobe higher than the noise upper limit rotational speed fan-noise, and thefinal rotational speed fan-final is:fan-final=min of(fan-n′,fan-noise).